Optical disk

ABSTRACT

The invention provides an optical disk that enables high-speed reproduction of address signals. A wobble address system for optical disk supports various types of synchronization, such as phase synchronization, bit synchronization, word synchronization, etc., to be established easily with high detection reliability with the use of an self-orthogonal code. Thus, the invention provides a method for easily synchronizing an address signal, i.e., high-speed reproduction of the address signal. Further, by virtue of an efficient modulation system of the address signal and redundancy thereof, it becomes possible to detect address information with high reliability. This capability is particularly effective in optical recording/reproduction with a blue light source whose signal light quantity and reproduction quality are prone to reduce. Moreover, other additional data of the address data is preserved in the wobbles, which provides medium information to a rewritable optical disk without using embossed pits such that a high-reliability disk (with enhanced security) is realized with a low cost and easily.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of nonprovisional U.S.Ser. No. 12/149,152 filed on Apr. 28, 2008, which is a Continuationapplication of nonprovisional U.S. Ser. No. 11/376,112 filed on Mar. 16,2006, which is a Continuation application of nonprovisional U.S. Ser.No. 10/979,171 filed on Nov. 3, 2004, which is a Continuation of U.S.Ser. No. 10/703,537 filed on Nov. 10, 2003, which is a Continuation ofU.S. Ser. No. 10/183,643 filed on Jun. 28, 2002. Priority is claimedbased upon U.S. application Ser. No. 12/149,152 filed on Apr. 28, 2008,which claims the priority date of U.S. application Ser. No. 11/376,112filed on Mar. 16, 2006, which claims the priority date of U.S.application Ser. No. 10/979,171 filed on Nov. 3, 2004, which claims thepriority date of U.S. application Ser. No. 10/703,537 filed on Nov. 10,2003, which claims the priority date of U.S. application Ser. No.10/183,643 filed on Jun. 28, 2002, which claims the priority date ofJapanese Patent Application 2001-213038 filed on Jul. 13, 2001, all ofwhich is incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a recording format for a high-capacityrewritable optical disk, more specifically to a method for arranging andpreserving addresses of recording area identification information,namely the addresses on the optical disk whose groove portions or landportions are allocated as recording tracks.

BACKGROUND OF THE INVENTION

An example of the track configuration of the conventional optical diskwill be described referring to FIG. 16. A plurality of groove tracks 11and land tracks 12 are arranged alternately in a radial direction of adisk-like recording medium. Each track is wobbled by a small amount inthe radial direction. Further, each track is divided into a plurality ofcircular arc sectors that are arranged in the radial direction, and in aleading part of each circular arc sector, a header 6 having addressinformation used for identifying a recording area is placed. The headers6 are arranged in the radial directions, i.e., are placed on radiallines. In this example, a width of each track is approximately 0.6 μmand a groove depth of each groove portion is approximately 60 nm. Inthis example, a length of the sector is approximately 6 mm, whichcorresponds to a user capacity of 2048 bytes. Each groove portion andeach land portion are wobbled by amplitude of approximately 20 nm in theradial direction. The period of the wobble is set at 1/232 times of thesector length, namely, approximately 25 μm. This ratio 1:232 is chosento correspond the period of the wobble to integral multiples of thelength of the record data (channel bit length) such that a recordingclock can easily be generated from the wobbles.

FIG. 16 shows details of a sector address header portion in a leadingpart of the track, namely, an identification information portion. InFIG. 16, pieces of the identification information are placed at twopositions, a first position 631 and a second position 632, that arealigned in the radial direction, on the radial lines. The track connectsto an immediately previous/subsequent track when making a round, i.e.,the groove portion 11 to the groove portion 11 and the land portion 12to the land portion 12. In this example, each identification informationitem corresponds to a recording area of an information track at itsright. Further, identification information corresponding to the groovepart information track 3 is placed at a first position 631, and theidentification information corresponding to the inter-groove partinformation track 4 is placed at a second position 632. That is, piecesof the identification information are placed in such a way that theposition thereof along the information track is different from those ofadjacent tracks but agree with those of adjacent-but-one tracks. Thatis, when viewing on boundary lines between the land track and the groovetrack, the placement position of the identification information isdivided into first and second areas, and the first and secondidentification information areas are used alternately one track by onetrack.

By this arrangement, for example, when the light spot 21 is scanned onthe groove portion 11, the pits on the one boundary line are alwaysreproduced to avoid the crosstalk among one track and the adjacenttracks. Therefore, it becomes possible that the address informationplaced on the prepits is reproduced without crosstalk. In this example,the address information of the prepits is recorded with an 8/16modulation code (channel bit length=0.14 μm).

The identification information in the header part is composed of smalldimples (pits), which are formed due to the unevenness of a substrate orthe like together with the grooves etc. when the disk is fabricated.

A phase change type recording film (GeSbTe) is used as a recording film,and a record mark is shaped as an amorphous region.

The foregoing conventional example is described in detail, for example,in Japanese Patent No. 2856390, etc.

However, in applying the above-mentioned conventional technique tohigh-density recording where recording/reproduction is performed with ablue light source, it was difficult to form small embossed pits in theheader parts. Further, the efficiency of the recording track (formatefficiency) is reduced because the header part has no grooves and cannotbe used as a recording area. Therefore, the prior art is disadvantageousin realizing large capacity in the optical disk.

Another example of conventional methods for recording the addressinformation by means of the wobbles of the groove portion withoutperforming the recording at the sector address header part is describedin the international standard ISO/IEC 16969.

In this example, the wobble groove that was frequency-modulated is usedin order to record the address data. One round of the disk is composedof about 3,000 wobbles, and 7.5 periods of the wobbles are used toexpress one bit of the address data. To express bit “1,” 4 periods ofthe 7.5 periods are specified as the first half and the other 3.5periods are specified as the second half. In other words, the first halfis the wobbles of a high frequency and the second half is the wobbles ofa low frequency. The frequency ratio is set at 8 to 7. Conversely, bit“0” is expressed by the 3.5-period low-frequency wobbles for the firsthalf, and the 4-period high frequency wobbles for the second half. A setof 48 address bits forms an address codeword. 14 bits of the 48 bits ofthe address codeword are parities for error detection and the leading 4bits are synchronization information used for establishingsynchronization with this codeword. The breakdown of these four bitsincludes 30 periods of the wobbles (4.times.7.5), i.e., 12-periodhigh-frequency wobbles, 3.5-period low-frequency wobbles, 4-periodhigh-frequency wobbles, and 10.5-period low-frequency wobbles. Thesynchronization information can be identified from other data due to thefact that, in the synchronization information, wobbles of the samefrequency longer than that of normal address bits by 4 periods or 3.5periods whereas in a boundary of the normal address bits, wobbles of thesame frequency only at 8-period (high-frequency) or 7-period(low-frequency) at most.

However, in the above-mentioned conventional technique, 1 address bit ofthe address data is expressed by 7.5-period wobbles and the differencein frequency between the first half part and the second half part is notlarge such that it is difficult to detect a boundary between the firsthalf part and the second half part with high precision by increments ofone unit of the wobble period based upon these wobbles. Further, sincethe synchronization information does not differ so much from otheraddress bits, it is highly likely to be detected mistakenly. Moreover,the parity in the address codeword is 14 bits at most, which issufficient only for checking errors but not for correcting errors suchthat the address information can not be reproduced if 1 bit in theaddress codeword is mistakenly detected It is necessary to securesufficient S/N of the medium in order to ensure the reliability ofaddress reproduction. When trying to apply this method to thehigh-density disk that needs the blue light source for reproduction, itis especially difficult to secure sufficient S/N because of the reducedefficiency of blue light detectors.

The first object of the present invention is to provide ahigh-performance optical disk such that the synchronization can beestablished easily for the address signal thereof so as to reproduce theaddress signal at a high speed.

The second object of the present invention is to provide an optical diskin which the address information that can be detected with highreliability.

The third object of the present invention is to provide a method forgiving necessary medium information to the rewritable optical diskwithout using the embossed pits that are difficult to form.

SUMMARY OF THE INVENTION

To achieve the objects of the present invention, the following meanswere used.

(1) In a proposed optical disk, at least one of a groove group includinga plurality of grooves and an inter-groove group including a pluralityof lands defined by the grooves in the form of a spiral or concentriccircles constitutes an information recording area. The optical disk isshaped in the following way. Either the groove group or the inter-groovegroup is displaced by a small amount in the radial direction accordingto a combined waveform formed by merging at least a synchronouscomponent of a constant frequency that is not modulated and a signalcomponent that is modulated according to the address data to be recordedin the information recording area.

The small displacement of the grooves, or the lands is usually calledthe wobble, and a waveform of this wobble can be easily detected by asignal tracking detector (e.g., a push-pull detector etc.). There are anunmodulated component and a modulated component in a detected wobblesignal. By using the unmodulated component, disk rotation velocitycontrol and phase synchronization between the phase locked loop (PPL)clock and the reproduced signal can be conducted, and by using themodulated component, the address information can be easily reproduced.

(2) It is specified that a frequency band of the modulated componentdoes not overlap the constant frequency of the unmodulated component.

For example, a waveform made by superposing of an unmodulatedfundamental wave and a second harmonic wave that is phase-modulated by180 degrees so as to easily separate the unmodulated component and theaddress information and surely detect both signals based upon theirfrequency difference with a bandpass filter, etc. As such, the firstobject of the present invention is achieved.

(3) It is recommended that the unmodulated component and the addressinformation are combined in a time-division multiplexing manner suchthat a period of the combined waveform is equal to or larger than aperiod of the wobbles and both components have substantially equalperiods in time domain.

For example, the unmodulated component is allocated to a front edge ofthe wobble and the modulated component is allocated to a rear edgethereof. By this arrangement, the synchronization can is performedstably with a PLL circuit for selectively detecting only the front edgeand the address information can be obtained by detecting a position ofthe rear edge.

As another example, a waveform consisting of three edges as a set may beused, wherein one edge remains unmodulated and the other two edges arephase-modulated. Further, as yet another example, the waveform may becomposed such a way that a degree of modulation is varied continuouslyfrom a modulated part (100%) to an unmodulated part (0%) such that themodulated part and the unmodulated part are allocated alternately andperiodically.

In any cases, since the phase synchronization information can beobtained stably by extracting the unmodulated signal component,regardless of the address information, fast synchronization at the timeof accessing becomes possible. As such, the first object of the presentinvention is achieved.

(4) In a proposed optical disk, at least one of a groove group and aninter-groove group in the form of a spiral or concentric circles isallocated as an information recording area. At least one of the groovegroup and the inter-groove group is wobbled in the radial direction.Pieces of information in the form of binary data or otherwise areassigned to plural kinds of unit wobble waveforms of a constant length.Further, a plurality of said unit wobble waveforms are placed to form awobble sequence. One bit of the address data or the user data isexpressed by at least two kinds of wobble sequences with differentarrangements.

For examples, waveforms such as those shown in FIG. 1( a) are used asthe plurality of wobble waveforms and one bit of the address data isexpressed by a wobble sequence formed by arranging a plurality of thesewaveforms. In this case, it is recommended that each of plural kinds ofwobble sequences be made to be as different as possible (that is, theyare made to be mutually different in a plurality of unit wobblewaveforms). This is because, if there are many differences between thewobble sequences, even when some of unit wobbles cannot be detected dueto an error, such as one caused by defect, the whole reproduced wobblesequence is checked to find which wobble sequence is closest to theoriginal such that the wobble sequence thus chosen is assumed to be thereproduced address data. The larger the difference among the wobblesequences, the more the acceptable number of the mistakenly detectedwobbles. Further, a longer wobble sequence (a wobble sequence having alarger number of unit wobble waveforms in it) has higher resistanceagainst erroneous detection. That is, the second object of the presentinvention is achieved.

(5) The wobble sequence is specified to be in an arrangement thatexhibits strong autocorrelation, i.e., selfcorrelation, for a shift byone length or more of the unit wobble waveform.

The strong selfcorrelation has the following property. When the wobblesequence is collated with a wobble sequence generated by shifting(shifting cyclically) per one or more unit wobble waveforms, all theunit wobbles naturally show agreements. The number of agreements isreduced even when there is a slightest shift.

As a wobble sequence having the above property, there is a wobblesequence that can be obtained by allocating different unit wobblewaveforms to “0” and “11” of a maximum period sequence (M-sequence)which length is limited by the total number of available registers.

A wobble sequence exhibiting strong selfcorrelation can make the PLLcircuit synchronize with the reproduced signal accurately with adeviation of less than the length of one unit wobble waveform. If thesynchronization to the unit wobble waveform is established by PLL, etc.,the synchronization for the unit of 1 bit of the wobble data can beexecuted for the unit of 1 clock of the phase lock loop (PLL). That is,the first object of the present invention is achieved.

If a plurality of wobble sequences are used to express the address bit,the cross-correlation between different wobble sequences (including ashifted sequence) is preferably as low as possible. That is, it isundesirable to choose a wobble sequence that is susceptible to bemistaken as a different wobble sequence to establish erroneoussynchronization. Preferably, the wobble sequence is selected such thatthe degree of the cross-correlation is kept two-thirds or less of thedegree of selfcorrelation.

(6) In a proposed optical disk, at least one of a groove group and aninter-groove group in the form of a spiral or concentric circlesconstitutes an information recording area. At least one of the groovegroup and the inter-groove group is wobbled in the radial direction. Aplurality of wobbles form the address codeword used for identifying theinformation recording area. Further, a plurality of wobble sequences forsynchronization are placed in the said address codeword

(In a proposed optical disk, at least one of a groove group and aninter-groove group in the form of a spiral or concentric circlesconstitutes an information recording area. At least one of the groovegroup and the inter-groove group is wobbled in the radial direction. Aplurality of wobbles form the address codeword used for identifying therecording area, and the address code is divided and placed in aplurality of synchronization frames that are partitioned by the wobblesequences used for synchronization.

The above means can establish synchronization in a time period shorterthan that is required to reproduce the address codeword itself. As such,the second object of the present invention is achieved.

Further, since plural pieces of synchronization information are placedin a single codeword, redundancy is provided for the synchronizationinformation itself such that, the reliability against loss and erroneousdetection of the synchronization information is ensured. Moreover, evenif synchronization is lost or tracking error occurs, its information canbe detected in a shorter time so as to ensure high reliability. Here adesirable arrangement is described.

(8) Preferably, the above-mentioned wobble sequence used forsynchronization is composed of plural kinds of arrangements, andpreferably such plural kinds of sequences are placed so that theirpositions in the address codeword can be specified with the differencein order or with the arrangement of the plural kinds of wobble sequencesplaced in the address codeword.

In other words, it is desirable that the synchronization information isnot of one kind but of plural kinds and pieces of the synchronizationinformation are placed in the codeword so as to be different accordingto its position therein. With this condition, the synchronization of thecodeword can be established by reproducing part of plural pieces ofsynchronization information in the codeword.

(9) In a proposed optical disk, at least one of a groove group and aninter-groove group in the form of a spiral or concentric circlesconstitutes an information recording area. At least one of the groovegroup or the inter-groove group is wobbled in the radial direction. Aplurality of wobbles form the address codeword used for identifying therecording area. Additional data other than the address information maybe placed in the said address codeword. Further, plural pieces ofadditional data placed in a plurality of address codewords areintegrated to form a code block for correcting errors of the additionaldata.

By this arrangement, necessary medium information etc. can be providedto the rewritable optical disk without using the embossed pits that aredifficult to form. As such, the third object of the present inventioncan be achieved. In this case, since the additional information is addedwith an error correction code, information can be surely reproduced evenvia a medium with a defect.

(10) The disk stores, as the above-mentioned additional data, controlinformation for protecting the data or cryptographic key information forrestricting accesses when the data is being recorded or reproduced; or

(11) The optical disk stores control information specifying a type ofdisk and characteristics thereof as the above-mentioned additional data.

These are pieces of information that are hitherto recorded usingembossed data in the prior art, but the present invention provides thesame benefits without using the embossed data so as to provideinexpensive disks.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of the presentinvention will become more apparent from the following detaileddescription considered with reference to the accompanying drawings inwhich like reference numerals designate like elements and wherein:

FIGS. 1( a) to 1(c) show one embodiment of the wobble waveform accordingto the present invention and a partially enlarged view of the opticaldisk for the present invention.

FIG. 2 shows the wobble waveform according to the embodiment of thepresent invention in FIG. 1.

FIG. 3 shows an example of a reproduction system of the wobble waveformaccording to the embodiment of the present invention in FIG. 1.

FIG. 4 shows another example of a reproduction method of the wobblewaveform according to the one embodiment of the present invention inFIG. 1.

FIG. 5 illustrates an effect of the reproduction system of the wobblewaveform according to the present invention.

FIG. 6 shows an example of compositions of the wobble sequencesaccording to the present invention.

FIG. 7 shows selfcorrelation functions and cross-correlation functionsof the wobble sequences according to the present invention.

FIG. 8 shows a composition of the synchronous frame according to thepresent invention.

FIG. 9 shows a composition of the address codeword according to thepresent invention.

FIG. 10 shows a composition of an error correction block for theadditional data according to the present invention.

FIG. 11 shows a block diagram of a recording/reproduction system of theoptical disk according to the present invention.

FIGS. 12( a) and 12(b) show an example of a wobble detection circuitaccording to the present invention.

FIG. 13 shows an example of compositions of the wobble sequencesaccording to the present invention.

FIG. 14 shows the selfcorrelation function and the cross-correlationfunction of the wobble sequence.

FIG. 15 shows an example of a composition of the wobble sequenceaccording to the present invention.

FIG. 16 shows the conventional optical disk format.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1( c) is an enlarged partial view of the optical disk according toone embodiment of the present invention. The information track iscomposed of a groove 11 provided in a spiral manner on a disk-shapedsubstrate. Information is not recorded on a land 12 in this embodiment.The track spacing (the distance between centers of adjacent grooves) is0.32 μm. The groove is provided on the substrate and the depth of thegroove is approximately 20 nm. It is assumed that therecording/reproduction is performed with an optical head whosewavelength is approximately 405 nm with a plurality of apertures ofapproximately 0.85 (as defined by the ratio of the lens aperture sizeand the focus length) in this embodiment. As such, this groove depth of20 nm is almost equal to an optical distance of 1/12 times wavelength.The grooved portion is wobbled in the radial direction by amplitude ofabout 15 nm. The wobble is recorded in sequence as shown in FIG. 1( c)corresponding to a waveform as shown in FIG. 1( b) which is formed byincorporating four kinds of unit wobble waveforms shown in FIG. 1( a).As shown in FIG. 1( b), when the waveforms are joined together, eitherof the waveforms in the upper and lower ranks of FIG. 1( a) is selectedsuch that the phase of the waveforms at a joining position isconsecutive. FIG. 1( c), illustrates, shortening the period of thewobble to exaggerate the amplitude of the wobble in the radial direction(the wobble amplitude is actually only about 5% of the track width).

The length of the unit wobble waveform of FIG. 1( a) is equivalent to 72channel bits of the recorded data. In this embodiment, the bit length ofuser data is approximately 0.11 μm and a run length limited (RLL) (1,7)code channel is used. The channel bit length is 0.073 μm. Therefore, thelength of the unit wobble waveform is approximately 5.2 μm.

Further, the unit wobble waveform is composed of one period of ahigh-frequency component and half of a period of a low-frequencycomponent, wherein frequency ratio of the high-frequency component andthe low-frequency component are set at 2:1. The characteristic of thewobble in this embodiment is that the unit wobble waveform alwayscomprises a wobble waveform of 1.5 periods. Therefore, a carrier signalwith 1.5 times the length of the unit wobble waveform is easilyreproduced.

FIG. 6 is a table showing the wobble sequence corresponding to theaddress data and a synchronization queue. In the figure, “1” and “0”correspond to a waveform 1 and a waveform 0 of FIG. 1, respectively. Asynchronization code A is specified to be a maximum period sequence(M-sequence) of a 31-bit length generated by a shift register of 5 bits,and a synchronous code B is a complementary sequence of the synchronouscode A. Further, data “0” is another M-sequence of a 31-bit length, anddata “1” is its complementary sequence.

The selfcorrelation functions and the cross-correlation functions ofthese four sequences in FIG. 6 are shown in FIG. 7. In finding thesecorrelation functions, the bit product of two sequences is set at 1 whencorresponding bits are in agreement and set at −1 when they are indisagreement, and the bit products are summed up for the length of thesequences. The selfcorrelation functions take on a value of 31 at shifts(between an address bit symbol and a reproduced sequence) of 0 and 31bits. The selfcorrelation functions at other shifts and thecross-correlation functions at all shifts take on values not more than11. The correlation function=/(the number of agreements)−(the number ofdisagreements). The correlation function is 11 or less means that thenumber of agreements is 21 or less and the number of disagreements is 10or more. In other words, there are disagreements in ten unit wobbles ormore (number of unmatched wobbles) in the all cases except when thesequence is compared with itself. It is easy to establish thesynchronization for the unit of 31 bits by utilizing the correlation. Toestablish the synchronization, what is required therefor is to check thecorrelation. A circuit (to be described later) shown in FIG. 12 is usedto check the correlation functions for every wobble shifts eachdiffering by 1 unit wobble, and to determine the synchronization to beestablished. For example, when the correlation function marks 27 ormore, since the maximum of the correlation function is 31, thedisagreement of up to (31−27)/2=2 bits are allowed in establishing thesynchronization. In this example, even if two of 31 unit wobbles cannotbe normally detected, the synchronization of the address bit can beestablished. On the other hand, if the synchronization is mistakenlydetermined to have been established when the synchronization has notbeen done, the error is restricted to (27−11)/2=8 bits or more at thesame time. If erroneous detection probability of the unit wobble is 1%(in reality, the erroneous detection probability is 0.1% or less), theprobability of a correlation function value not being 31 isapproximately 27%, whereas the probability of errors occurring in 2 bitsor more becomes as considerably low as 0.3% or so. The probability ofthe synchronization to be mistakenly determined as being established isas low as 10⁻⁴ (0.01%) or less, which turns into a level that does notcause any problem at all in practical applications.

The address data bits and the synchronous codes A, B each consisting of31 unit wobble waveforms as described above are placed, as shown in FIG.8, to form the address codeword (address word). FIG. 8 shows threeaddress words, wherein each address word is composed of four synchronousframes each having the length of 26 address bits. Arrows in the figureshow an order of the arrangement on the recording medium. Eachsynchronous frame is recorded by placing the synchronous codes A and Bof FIG. 6 in the leading part (at the first bit) and at the third bit,respectively, and placing the code sequences whose frame identificationnumbers are the data 0 and of the data 1 of FIG. 6 at the second bit andat the fourth bit, respectively. Remaining 22 bits are used for actual(address) data in this example. Based upon the synchronous codes andidentification codes, one of 8 synchronous codes is detected, one of 4identification numbers is allocated to the second bit, and another oneof the 4 identification numbers is allocated to the fourth bit. Aposition in the address word is ascertained when the detection of thesesynchronous codes occurs. That is, synchronization is establishedaccording to the address word. In this embodiment, there is sufficientredundancy of the data (the wobble sequence) to establish thesynchronization. The synchronization can therefore be established evenin the system using the blue light source with which no sufficient S/Nis ensured.

In this embodiment, the synchronous codes A and B are allocated in theleading part of respective synchronous frames. Alternatively, thesynchronous code A can be located in the leading part, and thesynchronous code B in a middle part of the synchronous frame such thateven if the tracking error occurs during the recording/reproduction, theloss of synchronization can be detected quickly.

FIG. 9 shows an arrangement of the data in the address word. As shown inFIG. 8, each address word is composed of 4 synchronous frames each ofwhich comprises a set of a 4-bit synchronous code and 22-bit addressdata. The data for address information becomes 88 bits consisting ofsummation of four of these 22-bit parts, i.e., 11 bytes. In thisembodiment, the leading 4 bytes (32 bits) of these are assigned to theaddress number, and 2 bytes (16 bits) are assigned to the parity (checkcode) for checking whether the address number is normally detected. Thischeck code is added only to the 4 bytes of the address number, aReed-Solomon code with a unit of 8-bit symbols. The probability formistakenly detecting the address number is significantly reduced withthis check code to about one 60-thousandth, which is sufficiently smallfor any practical applications. The additional data comprises five bytesof each address code.

In this embodiment, the additional data associated with 64 address wordsin total are made into a set to form the error correction block as shownin FIG. 10. Thus, the error correction code (“ECC”) of 5.times.12=60bytes is added to the data of 5.times.52=260 bytes for correcting aburst error extending over up to 6 address codes. The reliability of thereproduction of the additional data is sufficiently ensured.

In the above-mentioned example, 1 address codeword includes the userdata of 72.times.31.times.26.times.4=232128 channel bits. For a formatefficiency of about 85%, it occupies a length of about 16 KB of the userdata.

Embodiment 2

An example of an optical recording and reproducing apparatus that usesthe optical disk according to the embodiment 1 will be describedreferring to FIG. 11. FIG. 11 is a block diagram of the opticalrecording and reproducing apparatus that employs an optical recordingformat according to the present invention. Light emitted from a laserlight source 25 (wavelength is approximately 405 nm in this embodiment)that constitutes a part of the optical head 2 is collimated into avirtually parallel beam 22 through a collimator lens 24. The light beam22 is irradiated on the optical disk 11 through an objective lens 23 toform a spot 21, and subsequently guided to a servo detector 26 and apartition detector 27 through a beam splitter 28 and, a holographicelement 29, etc. Signals from the detectors undergo addition andsubtraction to become a tracking error signal and a focus error signal,which are input into the servo circuit. Based on the obtained trackingerror signal and focus error signal, the servo circuit controlspositions of the objective lens 23 and of the optical head 2 so as toposition the optical spot 21 at a target recording/reproduction area.The addition signal of the detector 27 is input to a signal reproductionblock 41 to be processed for filtering, frequency equalization, andsubsequently for digitizing by a signal processing circuit. Wobbleinformation of the grooves (i.e., the grooved portion) is detected as adifferential signal from the partition detector 27 and is input to awobble detection circuit 42 of the signal reproduction block 41. Thewobble detection circuit 42 generates a clock synchronizing with thewobble signal to function as a discriminator of the wobble waveform.

An example of the internal configuration of the wobble-signal detectingcircuit is shown in FIG. 12( a). The differential signal (push-pullsignal) from the partition detector 27 is first input to a bandpassfilter 421, where a signal band thereof is extracted. The filteredsignal is then input to a binarization circuit 422 and is binarized.

The binarized signal is input to a PLL circuit 425. The PLL circuit 425is composed of a voltage controlled oscillator (VCO) 426, a carriersignal generating circuit (frequency divider/multiplier circuit) 424,and a frequency phase comparator 423. In this embodiment, the VCO 426 isoscillated at a frequency of the channel clock and the frequency isdivided by 72.div.1.5=48 in the frequency divider 424 to generate acarrier signal. The carrier signal is compared with the binarized signalfor phase and frequency. Based on the comparison results, the rotationnumber of the optical disk and the oscillation frequency of the VCO 426are controlled. Consequently, the carrier signal in synchronization withthe wobble signal is generated.

The unit wobble waveforms (all consisting of 1.5 periods) of FIG. 1 are,as described above, of 72 channel clocks and hence the average period ofthe wobble is of 48 channel clocks. The length of a unit wobble waveformis set to be of 72 channel clocks by synchronizing with every 48thchannel clock whose frequency is divided by 48. In other words, theaverage frequency of the unit wobble waveforms equals to the channelclock frequency divided by 48.

In a reference-wave generating circuit 429, a waveform formed bybinarizing the waveform on the upper left hand side of FIG. 1( a) isused as a reference waveform. An exclusive-OR operation is performed onevery bit of this reference waveform and the binarized wobble signal tocalculate the correlation function, and the results are integrated for72 channel bits by an integrator. If no noise exists, the integrationresults are 72 on the upper left hand side of FIG. 1( a), 0 (lowerleft), 36 (upper right), and 36 (lower right). Therefore, it is possibleto determine that a waveform is the waveform 1 when the integrationresult is between 18 and 54 or the waveform 0 when the result isotherwise. This is a process of the so-called maximum likelihood methodwhereby the most likely waveform is determined such that the reliabilityagainst noises is extremely high.

A similar result can be obtained by setting the binarized data as 1 and−1 and by multiplying the binarized signal by the binarized waveforminstead of the above-mentioned exclusive OR. In this case, themultiplication and summation results become 72, −72, 0, 0 such that wecan determine the reproduced waveform as 1 when the output of thediscriminator circuit 428 is −36 to +36, and otherwise as 0.

The wobble waveform data detected as mentioned above is processed by theaddress bit detector circuit 43 to determine the kind of wobblesequence, and at the same time synchronization is performed on theaddress bit to detect the address bit.

FIG. 12( b) shows the configuration of the address-bit detectingcircuit.

Outputs 0,1 from the wobble detection circuit are input to the 31-bitshift register 431 and then compared with four kinds of patterns of theFIG. 6 one by one. In this case, comparing the pattern to the 31-bitdata with 0 shift is the same as the correlation function of FIG. 7.Since one of the four kinds of patterns appears each time when the31-bit data is input, the correlation function has a pulse-like peak atevery 31 bits. Therefore, “almost synchronization” is determined whenthe correlation function exceeds a certain threshold (e.g., 27) and“synchronization” is finally determined thereafter when the correlationfunction exceeds the value of 27 after 31 bits pass through thesynchronous circuit. In other words, the 31-bit period incurs betweenthe “almost synchronization” stage and the “synchronization” stage. Inaddition, performance and reliability of the synchronization is furtherincreased by introducing a switch of processing modes as follows: (1)before the establishment of the synchronization, a “continuity”processing mode in which the threshold is set at a relatively low valuebut the synchronization is determined to be established only when threeor more consecutive synchronization pulses have been detected, and (2)after the establishment of the synchronization, a “window” processingmode in which the threshold is set at a low value but any pulsesoccurring at a time other than specified times spaced by 31 bits fromthe time of the initial synchronizing pulse are ignored or the thresholdis set high for such pulses or the like.

Though there are four types of patterns, whether it is the synchronouscode or the data can be determined once either pattern A or B isdetected and the synchronization to the synchronous frames (FIG. 8) areestablished. The data 0 and the data 1 are completely reverse to eachother (complimentary), and the distance between the patterns (Hammingdistance) is 31 bits. Soft decision method is applied to decide the data1 or the data 0. Soft decision only uses a fact of which one of the data1 and the data 0 is closer to the result, namely, the decision by higherdegree of similarity. Consequently, the probability of erroneousdetection of the address bit is reduced considerably. Here, assumingthat the erroneous detection rate of the unit wobble waveform is 1%, theerroneous detection rate of the address bit becomes 10⁻⁵⁰ or less. As anextreme example, assuming that the erroneous detection rate of the unitwobble waveform is as bad as 5% (the worst condition), the erroneousdetection rate of the address bit is at the order of 10⁻¹⁴ which ensurespractically sufficient high reliability.

The detected address bit is subjected to address data decoding, such aserror decision etc., at the decoder circuit 46 and further to errorcorrection and decision processing (on the additional data).

The error correction processing on the additional data may be performedby a microprocessor for convenience.

Embodiment 3

Another embodiment according to the present invention will be describedreferring to FIG. 2.

This embodiment differs from the embodiment 1 in the unit wobblewaveform. In the embodiment 1, the unit wobble waveform is composed of1-period high-frequency component and half-period low-frequencycomponent, whereas in this embodiment unit wobble waveform is composedof half-period low-frequency component and half-period high-frequencycomponent. In this example, different from the embodiment 1, thefrequency ratio of the high-frequency component and that of thelow-frequency component is 1:1. The feature of the wobble according tothis embodiment is that the front edges are always located at both thefront end and the rear end of the unit wobble waveform which positionsdo not change at all regardless of the address data. Therefore, thewobble period of the unit wobble waveform is 1 period regardless of therecording waveform. The reproduction of waveform according to thepresent invention includes, for example, a method of confirming theexistence of the edge shown in FIG. 3 and a method of using a valueobtained by integrating the value of exclusive OR with the referencewaveform, which is identical to the embodiment 2, for the length of theunit wobble waveform in FIG. 4.

In the case of the method in FIG. 3, a recording/reproduction clock suchthat the length of the unit wobble waveform equals to three periods ofthe generated data, and the binarized data is detected at a timeinterval of the said clock. In FIG. 3, the binarized data is reproduced,for a unit of 3 channel bits such that “100” is converted into “0” and“110” is converted into “1.”

The method in FIG. 4 of the embodiment 3 is almost the same as theembodiments 1, 2. The address data is also detected by checking the dutycycle of the result of exclusive-OR processing (in the bottom row) onthe binarized data (in the second row, also in FIG. 2) and the referencedata (in the third row).

FIG. 5 shows the detecting scheme of FIG. 4 being robust against DCvariation of the wobble signal. When a DC level of a raw signal (theuppermost row) varies, although the duty ratio of the binarized signalchanges, the duty cycle exhibits almost no change by virtue ofexclusive-OR processing on it and the reference signal (in the thirdrow). That is, it is robust against to the low-frequency fluctuation ofthe reproduced (wobble) signal. This indicates that it exhibits highresistance to dominant fluctuation (noise), such as leakage of therecording data during data recording or after the data recording andcross talk of the wobbles of the adjacent track.

Embodiment 4

FIG. 13 shows an example where three kinds of M-sequences are used asthe wobble sequences according to the present invention and each of thesaid M-sequences is subjected to bi-phase modulation. For example, ifthis method is applied to a unit wobble waveform with a DC component asin the embodiment 3, the DC component can be diminished to zero, andconsequently the influences upon the reproduced signal and the servosignal are effectively eliminated.

The unit wobble waveform of FIG. 1 seems to have the DC component atfirst glance. However in a case of the example of FIG. 1, since the unitwobble waveforms each of which has two pairs of unit wobbles and isdifferent from each other such that the DC component are repeatedalternately, the DC component is not generated.

FIG. 14 shows the cross-correlation of the sequences of FIG. 13, whichexhibits excellent cross-correlation characteristics.

Embodiment 5

The unit wobble waveform of another embodiment according to the presentinvention is shown in FIG. 15. The wobble of this embodiment is formedby superposing 180-degree phase-modulated waveform with an angularfrequency of 2ω on the unmodulated fundamental waveform with an angularfrequency of ω.

Since the unmodulated component and the modulated component can beseparated with a suitable bandpass filter and a stable clock generatedfrom the modulated component can be used in reproducing the modulatedcomponent, this method is superior to the prior art in synchronizationcharacteristics and address information reproduction characteristics.

The optical disk according to the present invention can easily establishthe synchronization to the address signal in the wobble address systemthat is advantageous in the format efficiency so as to reproduce theaddress signal fast. Moreover, due to the efficient modulation system ofthe address signal and its redundancy, the address information can bedetected with high reliability. This effect is particularly effective inthe optical recording/reproduction performed with the blue light sourcewhose signal light quantity and reproduction quality are prone toreduce. Moreover, the wobble is specified to preserve other additionaldata in addition to the address information so as to provide mediuminformation to the rewritable optical disk without using the embossedpits. As such, a high-reliability disk (with enhanced security) can berealized at a low cost and easily. The preservation of the additionaldata by the wobble has been realized only after the introduction of thewobble with high detection efficiency according to the presentinvention.

The principles, preferred embodiments and modes of operation of thepresent invention have been described in the foregoing specification.However, the invention which is intended to be protected is not limitedto the particular embodiments disclosed. The embodiments describedherein are illustrative rather than restrictive. Variations and changesmay be made by others, and equivalents employed, without departing fromthe spirit of the present invention. Accordingly, it is expresslyintended that all such variations, changes and equivalents which fallwithin the spirit and scope of the present invention as defined in theclaims, be embraced thereby.

1. An information recording apparatus for recording information to an optical disk having a groove group including one or more spiral grooves and an inter-groove group including one or more lands defined by the grooves, at least one of which constitute an information recording area, wherein at least one of the groove group and the inter-groove group is wobbled in the radial direction, a plurality of wobbles form an address codeword for identifying the information recording area, and a plurality of wobble sequences for synchronization are placed in said address codeword.
 2. An information recording apparatus according to claim 1, wherein the address codeword is divided and placed in a plurality of synchronous frames that are partitioned by wobble sequences for synchronization.
 3. An information recording apparatus according to claim 1, wherein the address codeword has additional data other than address information of the information recording area, and plural pieces of additional data placed in a plurality of address codewords are integrated to form a code block for correcting errors of the additional data.
 4. An information recording apparatus according to claim 3, wherein the additional data include control information for protecting address data or cryptographic key information for restricting accesses to the address data.
 5. An information recording apparatus according to claim 3, wherein, the additional data include control information specifying a type of disk and characteristics thereof.
 6. An information recording apparatus according to claim 1, wherein the wobble sequences for synchronization comprises plural kinds of wobble sequences, and the plural kinds of wobble sequences are placed in the address codeword so as to specify a position in the address codeword with a difference in arrangement order of the plural kinds of wobble sequences placed in the address codeword. 